here is a continuing demand for semiconductor memory devices with higher density and low power consumption. Indeed, integration density and power are important factors that are considered when determining which type of memory to implement for a given application. Semiconductor memory devices include, for example, register files or CMOS static random access memory (SRAM). Other types of memory include DRAM (dynamic random access memory) devices. Although DRAM provides a high degree of integration, SRAM is typically preferred over DRAM because SRAM cells can operate at higher speeds and lower power dissipation than DRAM cells. Indeed, SRAM cells typically do not require refreshing and can store data indefinitely as long as such cells are powered. In contrast, DRAM cells must be periodically refreshed.
Register files are typically used in very high performance applications where several read and write ports enable data to be read and written into the file, simultaneously, by different functional units that access the same set of data during the same cycle. Since the register file cell uses many ports for reads and writes, it is typically much larger than a single port SRAM cell limiting the number of bits stored in the register file. Moreover, with low voltage applications, SRAM memories are susceptible to noise, thus decreasing the stability of the memory cells.